Several paint replacement films, or dry paint films, are commercially available for replacing liquid painting in automotive applications. These paint films are typically die-cut and incorporated on the structure of the automobile as appliqués. Such paint films include those disclosed in U.S. Pat. No. 5,759,477, assigned to Green Tokai Co. Ltd., Method of Making Film Plastic Parts; U.S. Pat. No. 7,833,380 B2, assigned to Laminate Products, Inc., Decorative System Composite and Method; U.S. Pat. No. 7,853,454 B2, assigned to Laminate Products, Inc., Method of Producing a Paint Film Part; U.S. Pat. No. 6,090,336, assigned to Decoma International Inc., Method for Manufacturing an Injection Molded Article with Outer Film Secured Thereto; and Plastics Technology January 2004: Where the Action is: Decorating with Formable Films, by Lilli Manolis Sherman. All of these US patents are incorporated herein by reference in their entirety.
The research activities on polymer coated metals predominantly focus on corrosion protection or corrosive delamination. In view of the inherent mismatch in properties between the polymer films and the metal, far less attention is given to the industrial forming of coated metals by means such as, for example, deep-drawing. Published papers deal with the loss of adhesion and recovery of polymer coated steel and laminated steel sheets sandwiched with a polymer core; however, there is virtually no history for the use of paint film laminated sheet metal in automotive stamping processes to produce complex three dimensional parts.
The author of Plastics Technology January 2004: Where the Action is: Decorating with Formable Films, L. Sherman, describes the advancements in the area of in-mold decorating (IMD) with paint films. This reference focuses on the production of film laminated plastic parts. The article quotes the industry manger at GE Plastics: “Paint line is the biggest investment in an auto assembly plant; it occupies half the plant floor space; and it can generate over 1500 tons a year of VOC's” (volatile organic chemicals).
The authors (page 477) of Journal of Materials Processing Technology 46 (1994) 455: Recent trends in sheet metals and their formability in manufacturing automotive panels, describe the need for development of forming techniques to overcome wrinkling and the deterioration of the appearance of the finished parts, and to increase the formable range. But they do not provide any solutions for satisfying this need.
The authors of Journal of Materials Processing Technology 151 (2004) 133-140: Wrinkling behavior of laminated steel sheets, disclose laminates created from a polymer core and sheets of metal on both sides of the polymer. The authors describe the behavior differences, as compared to homogeneous steel sheets, due to the significant differences in material properties of the steel and polymer.
The authors of Journal of Engineering Materials and Technology October 2007, Vol. 129, page 530: The Influence of Temperature on the Forming Behavior of Metal/Polymer Laminates in Sheet Metal Forming, describe the forming behavior of metal-polymer laminates for which a polymer is sandwiched between layers of metal. Although the constructions offer benefits in terms of weight reduction and vibration damping, when compared to the results for homogeneous metals the constructions are inferior in terms of the tendency to wrinkle.
The authors of Journal of Materials Processing Technology 209 (2009) 297-302: On the prediction of delamination during deep-drawing of polymer coated metal sheet, highlight the value of forming polymer coated sheet metal: decrease the subsequent steps of coating, increase cost savings, and eliminate VOC emissions. They further describe that deep-drawing produces large plastic strain. This strain produces rough surfaces and loss of adhesion, which may further result in delamination. They do not provide any solutions to these problems.
U.S. Pat. No. 4,225,553, assigned to Toyo Seikan Kaisha, Limited, discloses a method of manufacturing low-rigid, wrinkle free articles. The laminate construction cannot be more than 200 microns in thickness and consists of a thermoplastic resin film, aluminum foil, and a heat-sealable resin film. Drawing of this laminate is performed through cold-drawing—without a heating step.
U.S. Pat. No. 5,093,208, assigned to CMB Food can plc, discloses a process for laminating a metal sheet with a non-crystalline polyester film. The construction is useful for drawing into cans.
U.S. Pat. No. 6,699,566 B2, assigned to Alcan Technology and Management Ltd., discloses a process for manufacturing shaped packaging. Cold drawing is used in the process. The claims limit the thickness of the metal layer to 8-150 microns and the thickness of the plastic layer to 12-120 microns.